Testing fixture for vehicle impact simulation

ABSTRACT

A fixture includes a vehicle body and a tube connected to the vehicle body. The tube has an axis, and the fixture includes a piston slideably disposed in the tube along the axis. A seat belt D-ring is mounted to the piston. The tube and the piston each define holes positioned to be aligned with each other when the piston is in multiple positions along the axis in the tube. A pin is engageable with the holes when the holes are aligned.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part of and claims priorityto and all advantages of U.S. patent application Ser. No. 14/613,868filed on Feb. 4, 2015, which is herein incorporated by reference in itsentirety.

BACKGROUND

A vehicle impact may be simulated for the purpose of testing componentsof the vehicle such as seat mounts, seat components, seat belts,airbags, etc. For example, a vehicle rollover, a vehicle frontal impact,a vehicle side impact, etc., may be simulated. In the example of avehicle rollover simulation, the vehicle, or a portion of the vehicle,such as the body-in-white, may be placed in a cage and the cage may berolled to simulate a rollover. Specifically, the cage may be placed on amovable platform, which is moved along a track. Brakes are applied toabruptly stop the platform, at which time the cage rolls off of theplatform and continues to roll to simulate a vehicle rollover. Suchtests may be referred to as rollover component tests.

The cage allows for simulation of the vehicle rollover while preventingdamage to the exterior of the vehicle during the simulation. Since theexterior of the vehicle is not damaged during the simulation of thevehicle rollover, the exterior of the vehicle, e.g., the body-in-white,may be re-used in repeated vehicle rollover simulations.

However, during an accidental vehicle rollover, portions of the exteriorof the vehicle may deform. Since the cage protects the exterior of thevehicle during the vehicle rollover simulation, the rollover simulationin the cage does not simulate this exterior deformation. For example,the B-pillar of the vehicle, which supports a D-ring of a front seatbelt, may deform during an accidental rollover. This deformation of theB-pillar during the rollover moves the D-ring of the front seat belt. Assuch, this aspect of the operation of the front seat belt is notportrayed during the rollover simulation in the cage.

In the example, of a vehicle frontal impact, the vehicle, or a portionof the vehicle, such as the body-in-white, may be placed in a cage on asled buck. The sled buck may be accelerated and decelerated to simulatea vehicle frontal impact. The use of the cage and the sled buck allowsthe vehicle frontal impact to be simulated without damaging a vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cage and a vehicle for simulatingvehicle rollover.

FIG. 2 is a perspective view of a portion of the vehicle in the cagewith a testing fixture in a retracted position.

FIG. 3 is a perspective view of the cage and the vehicle during asimulated vehicle rollover.

FIG. 4 is a perspective view of a portion of the vehicle in the cageduring the vehicle rollover including the testing fixture in an extendedposition.

FIG. 5 is an exploded view of the testing fixture.

FIG. 6 is a side view of the testing fixture with a piston between aretracted position and an extended position.

FIG. 7 is another side view of the testing fixture with the piston inthe retracted position.

FIG. 8 is a perspective view of a sled buck including a vehicle and acage for simulating a vehicle frontal impact.

FIG. 9 is an exploded view of a second embodiment of the testingfixture.

FIG. 10 is a side view of the second embodiment of the testing fixturewith the piston fixed to a tube in a first example position.

FIG. 11 is a side view of the second embodiment of the testing fixturewith the piston fixed to the tube in a second example position.

FIG. 12 is an exploded view of a third embodiment of the testingfixture.

FIG. 13 is a side view of the third embodiment of the testing fixturewith the piston fixed to the tube in a first example position.

FIG. 14 is a side view of the third embodiment of the testing fixturewith the piston fixed to the tube in a second example position.

DETAILED DESCRIPTION

With reference to the Figures, wherein like numerals indicate like partsthroughout the several views, a testing device 10, 11 is shown. A firstembodiment of the testing device 10 is shown in FIGS. 1-4, and may beused to simulate a vehicle rollover, as described below. A secondembodiment of the testing device 11 is shown in FIG. 8, and may be usedto simulate a vehicle frontal impact. Common numerals are used in thefigures and this detailed description identify common features of thetesting device 10 and the testing device 11.

With reference to FIGS. 1 and 8, the testing device 10, 11 includes acage 12 for supporting a vehicle 14. With reference to FIGS. 1-4, thetesting device 10 includes a testing fixture 16 for mounting to thevehicle 14. A second embodiment of the testing fixture 116 is shown inFIGS. 10-12, and a third embodiment of the testing fixture 216 is shownin FIGS. 12-14. As shown in FIG. 8, the testing device 11 may includethe second embodiment of the testing fixture 116 may be mounted to thevehicle 14. Alternatively, the testing device 11 may include the firstembodiment of the testing fixture 16 or the third embodiment of thetesting fixture 216. In other words, any one of the testing fixtures 16,116, 216 may be used in the testing device 11 to simulate a vehiclefrontal impact. Common numerals are used in the figures and thisdetailed description to identify common features of the testing fixture16, the testing fixture 116, and the testing fixture 216.

With reference to FIGS. 1-4, as set forth further below, the cage 12 maybe rolled while the vehicle 14 is disposed in the cage 12 to simulate avehicle rollover. The cage 12 simulates the vehicle rollover andprevents damage to the exterior of the vehicle 14 during the simulation.Since the exterior of the vehicle 14 is not damaged during thesimulation of the vehicle rollover, the vehicle 14 may be re-used inrepeated vehicle rollover simulations.

With reference to FIG. 8, as set forth further below, a sled buck 82includes the cage 12 and the vehicle 14. The testing fixture 11 includesthe sled buck 82 and a testing fixture 16, 116, 216. The sled buck 82may be engaged with rails 84 mounted to the floor, and the sled buck 82may be accelerated and decelerated, e.g., with motors, barriers, etc.,to simulate a vehicle frontal impact. The use of the sled buck 82 allowsthe vehicle frontal impact to be simulated without damaging a vehicle,and the vehicle 14 may be re-used in repeated vehicle frontal impactsimulations.

With reference to FIGS. 1-4, 8, and 12, the testing fixture 16, 116, 216supports a D-ring 18 of a front seat belt 20 adjacent a pillar 22 of thevehicle. The testing fixture 16, 116, 216 moves the D-ring 18 during thesimulation. For example, for a vehicle rollover simulation, the vehiclerollover in the cage 12 simulates deformation of the pillar 22 during avehicle rollover, as set forth further below. As also set forth furtherbelow, the testing fixture 16, 116, 216 may be adjusted to simulatepillar deformation, seat belt height, etc., and/or associated movementof the D-ring 18 during a simulation.

With reference to FIGS. 5-7, the testing fixture 16 includes a tube 24and a piston 26 slideably disposed in the tube 24. An actuator 28 issupported on the tube 24 in communication with the piston 26 through thetube 24. A ratchet 30 is supported on the tube 24 and engaging thepiston 26 for preventing movement of the piston 26 into the tube 24.

The piston 26 is initially in a retracted position relative to the tube24, as best shown in FIGS. 2 and 7. During the vehicle rolloversimulation, the actuator 28 is activated to extend the piston 26 fromthe tube 24 to an extended position, as shown in FIG. 4. The ratchet 30is configured to allow movement of the piston 26 toward the extendedposition and to prevent movement of the piston 26 into the tube 24,i.e., toward the retracted position, to simulate the vehicle rollover.In other words, after the piston 26 moves to the extended position, theratchet 30 retains the piston 26 in the extended position to simulatethe permanent deformation of the pillar 22 during the vehicle rollover.

With reference to FIGS. 5-7, the tube 24 defines a chamber 32 receivingthe piston 26. The chamber 32 may extend along an axis A and the piston26 may extend from the retracted position to the extended position alongthe axis A.

The tube 24 may include one or more flanges 34 for fixing the tube 24 tothe vehicle and/or the cage 12. For example, the flanges 34 areconnected to the vehicle 14 with threaded nuts and bolts, as shown, forexample, in FIG. 2. Alternatively, the flanges 34 may be connected tothe vehicle and/or the cage 12 in any suitable fashion.

The tube 24 may be formed of metal, such as steel. Alternatively, thetube 24 may be formed of any suitable material.

The piston 26 may be configured to slide relative to the tube 24 in thechamber 32 from the retracted position to the extended position. Thepiston 26 and the chamber 32 may have a common cross-sectional shape tofacilitate sliding of the piston 26 in the chamber 32. For example, thepiston 26 and the chamber 32 have a rectangular cross-section in theFigures. Alternatively, the piston 26 and the chamber 32 may have anysuitable cross-sectional shape to facilitate sliding of the piston 26 inthe chamber 32.

As set forth above, the piston 26 supports the seat belt D-ring 18.Specifically, with reference to FIGS. 5-7, the piston 26 may include amounting surface 36 and the piston 26 may be mounted to the mountingsurface 36. The piston 26 may define a hole 38 in the mounting surface36 for receiving a fastener 40 (shown in FIGS. 2 and 4) connected to theseat belt D-ring 18. The hole 38 and the fastener 40 may be threaded,for example.

The piston 26 may include a plate 42 disposed adjacent to the D-ring 18,as shown in FIGS. 2 and 4. The plate 42 may support an accelerometer(not shown) for measuring acceleration of the D-ring 18 as the D-ring 18moves from the retracted position to the extended position.

The piston 26 may be formed of metal, such as steel. Alternatively, thepiston 26 may be formed of any suitable material.

The tube 24 may define a slot 44 which may, for example, extend alongthe axis A. A stopping pin 46 may be engaged with the piston 26 and theslot 44 may receive the stopping pin 46. The stopping pin 46 moves alongthe axis A toward an end 48 of the slot 44 as the piston 26 moves fromthe retracted position toward the extended position. When the piston 26reaches the extended position, the stopping pin 46 engages the end 48 ofthe slot 44 to stop the piston 26 in the extended position. As set forthabove, and as described further below, the ratchet 30 engages the piston26 when the piston 26 is in the extended position to prevent the piston26 from moving along the axis A toward the retracted position.

With continued reference to FIGS. 5-7, the piston 26 defines a pluralityof holes 50 along the slot 44 for alternatively receiving the stoppingpin 46. One or more of the holes not receiving the stopping pin 46 mayreceive a shear pin 80, as shown in FIGS. 5-6. When the piston 26 isdisposed in the chamber 32, the holes 50 are spaced from each otheralong the axis A. When the piston 26 is in the retracted position, theholes 50 may be exposed through the slot 44 so that the stopping pin 46may be engaged with one of the holes 50. Any one of the holes 50 may beengaged with the stopping pin 46 to choose the length of the extensionof the piston 26 from the tube 24 in the extended position.

The holes 50 may extend through the piston 26. In such a configuration,the stopping pin 46 may extend through one of the holes 50 and retainedin the hole 50 by a fastener 52. For example, the stopping pin 46 may bethreaded and may receive a threaded nut to fix the stopping pin 46 inthe selected hole. The fastener 52 may, alternatively, be any suitabletype of fastener, e.g., a cotter pin, a cap, etc.

One or more shear pins 80, shown in FIGS. 5-6, may be engaged with theholes 50. The shear pins 80 may be configured to be frangible when theactuator 28 is activated. Specifically, the shear pins 80 may be used totune the movement of the piston 26 from the retracted position to theextended position. For example, the shear pins 80 may slow the movementof the piston 26 toward the extended position to a desired acceleration.The shear pins 80 may be formed of any suitable material type, materialgrade, and diameter. As examples, the shear pins 80 may be formed ofaluminum, stainless steel, steel, etc. One or more shear pins 80 of thesame or different material type, material grade, and/or diameter may beengaged with the holes 50 to tune the movement of the piston 26 when theactuator 28 is activated. Two shear pins 80 are shown in FIGS. 5-6,however, it should be appreciated that any number of shear pins 80 maybe engaged with any number of respective holes 50.

One or more shear pins 54 may engage the tube 24 and the piston 26 totemporarily retain the piston 26 in the retracted position.Specifically, with reference to FIG. 5, the tube 24 may define one ormore holes 56 and the piston 26 may define one or more holes 58 thatalign with each other when the piston 26 is in the retracted position.The shear pin 54 may be engaged with the holes 56, 58 to retain thepiston 26 in the retracted position. FIG. 6 shows the piston 26 betweenthe retracted position and the extended position.

The shear pin 54 is configured to be frangible when the actuator 28 isactivated. As such, the shear pin 54 prevents movement of the piston 26relative to the tube 24 prior to the rollover simulation and, during therollover simulation, the actuator 28 breaks the shear pin 54 and forcesthe piston 26 toward the extended position. As set forth above, thestopping pin 46 stops the piston 26 in the extended position and theratchet 30 retains the piston 26 in the extended position.

The number and location of shear pins 54 engaged with the tube 24 andthe piston 26 may be selectively chosen based on the desired shear forcerequired to break the shear pins 54. For example, in the configurationshown in the Figures, the piston 26 and the tube 24 each define a pairof corresponding holes 56, 58. In this configuration, one shear pin 54may be engaged in either of the corresponding holes 56, 58, or two shearpins 54 may both corresponding holes 56, 58, depending on the desiredshear forces. The shear force required to break the shear pins 54 mayalso be modified by modifying the thickness and material type of theshear pins 54.

The actuator 28 may be a gas inflator. In such a configuration, the gasinflator may be in communication with the chamber 32 and, uponactivation, may introduce pressurized gas into the chamber 32 to forcethe piston 26 to the extended position. The piston 26 may be sealed tothe tube 24 along the chamber 32 such that the chamber 32 is gas-tight.The actuator 28 may, alternatively, be of any suitable type includingmechanical, hydraulic, pneumatic, etc.

With continued reference to FIGS. 5-7, the tube 24 may define a pressureport 60. In the configuration where the actuator 28 is the gas inflator,the pressure port 60 may be selectively opened or closed to control adesired amount of pressure in the chamber 32 from the gas inflator. Thetesting fixture 16 may include a pressure sensor (not shown) in thechamber 32 for measuring the pressure in the chamber 32 duringactivation of the actuator 28.

The actuator 28 may be fixed to the tube 24. For example, as shown inFIGS. 5-7, the actuator 28 may be bolted to the tube 24 with a bolt.

As set forth above, the ratchet 30 engages the piston 26 to allowmovement of the piston 26 toward the extended position and to preventmovement of the piston 26 toward the retracted position. As such, whenthe actuator 28 is activated to move the piston 26 from the retractedposition to the extended position, the ratchet 30 retains the piston 26in the extended position to simulate a permanently deformed pillar ofthe vehicle.

The ratchet 30 may include a pawl 62 pivotally mounted to tube 24. Thepawl 62 may be pivoted about a pin, for example. The ratchet 30 mayalternatively be of any suitable configuration for allowing the piston26 to move toward the extended position and preventing movement of thepiston 26 toward the retracted position.

The piston 26 may define teeth 66 engaged by the pawl 62. The teeth 66extend upwardly from a base 68 and include a forward surface 70 angledat an obtuse angle θ relative to the base 68 and a rearward face 72angled at an acute angle A relative to the base 68. In other words, theteeth 66 have a saw-tooth pattern. The pawl 62 may be shaped to matchthe angles of the forward face 70 and the rearward face 72. As such, theobtuse angle θ between the forward face 70 and the base 68 allows theforward face 70 to slide along the pawl 62 when the actuator 28 urgesthe pawl 62 toward the extended position. The acute angle A between therearward face 72 and the base 68 wedges the pawl 62 against the rearwardface 72 of the piston 26 is urged toward the retracted position, thuspreventing movement of the piston 26 toward the retracted position.

The ratchet 30 may include a spring 74 between the pawl 62 and the tube24. The spring 74 urges the pawl 62 into engagement with the teeth 66.As the actuator 28 moves the piston 26 toward the extended position, thepawl 62 rotates about the pin 64 as the forward face slides along thepawl 62. During this movement, the spring 74 urges the pawl 62 intoengagement with the teeth 66. When the piston 26 is in the extendedposition, the spring 74 urges the pawl 62 against the teeth 66 tomaintain engagement of the pawl 62 with the rearward surface 72 in theevent the piston 26 is urged toward the retracted position.

With reference to FIG. 1, during the simulation of the vehicle rollover,the cage 12 may be placed on a sled 76, which is moved along a track(not shown). Brakes are applied to abruptly stop the sled 76, at whichtime the cage 12 rolls off of the sled 76 and continues to roll tosimulate a vehicle rollover. The cage 12 protects the exterior of thevehicle 14 during the vehicle rollover simulation. The vehicle 14 usedin the test may, for example, be the vehicle body-in-white, i.e., theframe and body panels. Alternatively, the vehicle 14 used in the testmay include more or less features than the vehicle body-in-white.

As set forth above, during the vehicle rollover simulation, the actuator28 is activated to move the piston 26 relative to the tube 24 from theretracted position to the extended position to simulate deformation ofthe pillar 22 to which the seat belt D-ring 18 is attached. When theactuator 28 is activated, the actuator 28 breaks the shear pins 54 andforces the piston 26 toward the extended position. As the piston 26moves toward the extended position, the ratchet 30 rides along theforward faces 70 of the teeth 66. When the piston 26 reaches theextended position, the stopping pin 46 engages the end 48 of the slot 44to stop the piston 26 in the extended position. When the piston 26reaches the extended position, the ratchet 30 engages the teeth 66, andspecifically engages the rearward face of a tooth 66, to lock the piston26 in the extended position to simulate deformation of the pillar 22 andthe associated movement of the D-ring 18.

In FIGS. 1 and 3, the testing fixture 16 is shown mounted to theB-pillar 22. Alternatively, the testing fixture 16 may be mounted to anysuitable pillar 22 of the vehicle to simulate the deformation of thatpillar 22 and the resulting movement of the D-ring 18 mounted to thatpillar 22. The testing fixture 16 may be used for any suitable testincluding rollover tests such as rollover component tests, curb triptests, laterally tripped full vehicle tests, etc.

With reference to FIGS. 2 and 4, the seat belt 20 includes the D-ring 18and a belt 78, i.e., webbing 78, supported by the D-ring 18. The D-ring18 supports the belt 78 such that the belt 78 extends across theshoulder of the occupant, as shown with the crash-test dummy in FIG. 1.It should be appreciated that the seat belt 20 may include a retractor(not shown) mounted to the seat or the body of the vehicle 14. A freeend (not shown) of the belt 78 is also connected to the seat or the bodyof the vehicle 14. During the rollover simulation, the retractor and thefree end of the seat belt 20 are connected to the seat and/or the bodyof the vehicle 14.

The testing fixture 16 may include an accelerometer (not shown) formeasuring the acceleration, velocity, and displacement of the D-ring 18during the test. The accelerometer may, for example, be attached to theplate 42 on the piston 26.

With reference to FIGS. 9-11, the tube 24 may define several holes 56and the piston 26 may define several holes 58 that align with each otheras the piston 26 slides in the tube 24. Specifically, the tube 24 has anaxis A, and the piston 26 is slideably disposed in the tube 24 along theaxis A. The holes 58 in the piston 26 are spaced from each other along aline parallel to the axis A, and the holes 56 in the tube 24 are spacedfrom each other along a line parallel to the axis A.

The testing fixture 116 may be used with both the testing device 10 andthe testing device 11, i.e., in a vehicle rollover simulation and avehicle frontal impact. When used in the testing device 10, the testingfixture 116 may be operated as described for the testing fixture 16above. When used with the testing device 10, i.e., in a vehicle rolloversimulation, the testing fixture 116 is dynamic, i.e., the actuator 28and ratchet 30 operate as described above.

When used in the testing device 11, the texting fixture 116 may bestatic. In other words, the actuator 28 is not operated during thevehicle frontal impact simulation.

With reference to FIGS. 9-11, the testing fixture 116 includes a pin 55engageable with the holes 56, 58 when the holes 56, 58 are aligned.Specifically, as the piston 26 is slid along the axis A of the tube 24,at least some of the holes 56, 58 align with each other. The piston 26may be slid relative to the tube 24 to align the holes 56, 58 with eachother at a position along the axis A suitable for the simulation beingperformed. When this desired position is reached, the pin 55 is engagedwith any one of the pair of aligned holes 56, 58 to fix the piston 26relative to the tube 24. The pin 55 is removeable from the pair ofaligned holes 56, 58. This allows the pin 55 to be removed and thepiston 26 after the simulation to be adjusted relative to the tube 24for future simulations.

The pin 55 is designed to maintain the piston 26 fixed to the tube 24during a vehicle frontal impact simulation. In other words, the pin 55is sized, shaped, and/or of a suitable material such that the pin 55does not break during the vehicle frontal impact simulation. Thisensures that the D-ring 18 is held at a fixed position relative to thepillar 22 to simulate a vehicle frontal impact. In addition to engagingthe pin 55 with a pair of aligned holes 56, 58, another pin 55 may beengaged with another pair of aligned holes 56, 58 to strengthen theconnection between the piston 26 and the tube 24 to ensure that thepiston 26 and the tube 24 remain fixed to each other during thesimulation.

With reference to FIGS. 12-14, the testing fixture 216 may be used withthe testing device 11, i.e., in a vehicle frontal impact simulation.When used in the testing device 11, the texting fixture 116 may bestatic. The testing device 11 does not include the actuator 28 describedabove, and the piston 26 remains fixed relative to the tube 24 duringthe vehicle frontal impact simulation.

The tube 24 of the testing fixture 216 may define several holes 56 andthe piston 26 may define several holes 58 that align with each other asthe piston 26 slides in the tube 24. Specifically, the tube 24 has anaxis A, and the piston 26 is slideably disposed in the tube 24 along theaxis A. The holes 58 in the piston 26 are spaced from each other along aline parallel to the axis A, and the holes 56 in the tube 24 are spacedfrom each other along a line parallel to the axis A. The tube 24 of thetesting fixture 216 may include a continuous wall, i.e., without theslot 44, in which the holes 56 are defined.

With continued reference to FIGS. 12-14, the testing fixture 216includes a pin 55 engageable with the holes 56, 58 when the holes 56, 58are aligned. Specifically, as the piston 26 is slid along the axis A ofthe tube 24, at least some of the holes 56, 58 align with each other.The piston 26 may be slid relative to the tube 24 to align the holes 56,58 with each other at a position along the axis A suitable for thesimulation being performed. When this desired position is reached, thepin 55 is engaged with any one of the pair of aligned holes 56, 58 tofix the piston 26 relative to the tube 24. The pin 55 is removeable fromthe pair of aligned holes 56, 58. This allows the pin 55 to be removedand the piston 26 after the simulation to be adjusted relative to thetube 24 for future simulations.

The pin 55 is designed to maintain the piston 26 fixed to the tube 24during a vehicle frontal impact simulation. In other words, the pin 55is sized, shaped, and/or of a suitable material such that the pin 55does not break during the vehicle frontal impact simulation. Thisensures that the D-ring 18 is held at a fixed position relative to thepillar 22 to simulate a vehicle frontal impact. In addition to engagingthe pin 55 with a pair of aligned holes 56, 58, another pin 55 may beengaged with another pair of aligned holes 56, 58 to strengthen theconnection between the piston 26 and the tube 24 to ensure that thepiston 26 and the tube 24 remain fixed to each other during thesimulation.

As shown in FIG. 12, the seat belt D-ring 18 is mounted to the piston26. The seat belt 20 includes seat belt webbing 78 (shown, for example,in FIG. 2) connected to the body of the vehicle 14 and engaged with theD-ring 18. Specifically, the seat belt webbing 78 extends through a slotin the D-ring 18.

he disclosure has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation. Manymodifications and variations of the present disclosure are possible inlight of the above teachings, and the disclosure may be practicedotherwise than as specifically described.

What is claimed is:
 1. A fixture comprising: a vehicle body; a tubeconnected to the vehicle body and having an axis; a piston slideablydisposed in the tube along the axis; a seat belt D-ring mounted to thepiston; the tube and the piston each defining holes positioned to bealigned with each other when the piston is in multiple positions alongthe axis in the tube; and a pin engageable with the holes when the holesare aligned.
 2. The fixture as set forth in claim 1 further comprisingseat belt webbing connected to the vehicle body and engaged with theD-ring.
 3. The fixture as set forth in claim 1 further comprising teethon the piston and a ratchet supported on the tube and engaging the teethof the piston for preventing movement of the piston into the tube. 4.The fixture as set forth in claim 3 wherein the ratchet includes a pawlpivotally mounted to tube.
 5. The fixture as set forth in claim 4further comprising a spring between the pawl and the tube.
 6. Thefixture as set forth in claim 1 further comprising an actuator supportedon the tube in communication with the piston through the tube.
 7. Thefixture as set forth in claim 6 wherein the actuator is a gas inflatorand wherein the tube defines a chamber receiving the piston, the chamberbeing in communication with the gas inflator.
 8. The fixture as setforth in claim 1 wherein the tube defines a slot and the piston definesadditional holes along the slot with a stopping pin engaged with one ofthe additional holes.
 9. The fixture as set forth in claim 1 wherein thepin is designed to maintain the piston fixed to the tube during avehicle frontal impact simulation.
 10. The fixture as set forth in claim1 wherein the holes in the piston are spaced from each other along aline parallel to the axis, and wherein the holes in the tube are spacedfrom each other along a line parallel to the axis.